Key member for use in insertion or removal of a fuel rod of a nuclear fuel assembly grid

Abstract

A key member, a method for insertion and/or removal of the fuel rods in a nuclear fuel assembly using the key member and a method of disassembling the nuclear fuel assembly using the same key member are disclosed. The key member has first projections and second projections formed on the opposite faces of an elongated key body. In the insertion or removal of the fuel rods or in the disassembling the nuclear fuel assembly, the key member is inserted into the grid and rotated to bring the first projections and the second projections into engagement with the straps of the grids and the springs on the straps to thereby deflect the springs in a direction away from the dimples opposing the springs. In this situation, the insertion and removal of the fuel rods can be carried out. Further, in disassembling the nuclear fuel assembly, space required for inserting the key member into the grids may be ensured by subjecting prescribed portions of control rod-guide pipes and instrumentation pipes to cutting work and bulging the cut ends to move the cut end away from that of the opposing cut ends of the cut piece. The space may be formed by removing the control rod-guide pipes and instrumentation pipes after having formed slits in the pipes.

What is claimed is: 
     
       1. A key member for use in insertion and removal of a fuel rod into and from a nuclear fuel assembly grid which includes a plurality of elongated straps intersecting generally perpendicular with each other to define a plurality of grid cells therein, and a plurality of pairs of dimples and springs formed on the straps for supporting a plurality of fuel rods such that each pair of dimple and spring are disposed in facing relation to each other, and which includes key member accommodating openings formed at the intersections of the straps so as to define peripheral ends therearound, said key member comprising an elongated key body having a pair of opposite surfaces, said key body including a plurality of first projections adapted to be held in engagement with said peripheral end of said opening of said strap and a plurality of second projections adapted to be held in engagement with said spring to deflect the spring away from the dimple facing thereto, said first projections and said second projections being formed on said opposite surfaces alternately in a staggered relation to one another.